Meeting Abstract

P3.144  Monday, Jan. 6 15:30  Acute and chronic alterations in atmospheric oxygen do not alter femoral biomechanics in Alligator mississippiensis LUJAN, SL; OWERKOWICZ, T; ELSEY, RM; HICKS, JW; MIDDLETON, KM*; CSU San Bernardino; CSU San Bernardino; Rockefeller Nat. Wildlife Refuge; UC Irvine; University Missouri-Columbia middletonk@missouri.edu

Analyses of the microanatomy and cross sectional geometry of limb bones are often used to infer growth, locomotor ability, and life history strategies of fossil vertebrates. Although atmospheric oxygen has varied widely in the past, studies of extant relatives are typically carried out in a normoxic environment. Because acute hypoxia and hyperoxia have been shown to affect the growth of in a variety vertebrates, the utility of comparisons between extinct and extant taxa has been questioned. We studied the American alligator, Alligator mississippiensis, to test for effects of environmental oxygen on skeletal growth and biomechanics. Eggs were incubated and hatchlings reared in one hypoxic and three hyperoxic conditions. At regular intervals from 2 to 104 weeks, alligators were sacrificed and femora prepared for analysis. Undecalcified specimens were dehydrated, and morphometric whole-bone measurements taken prior to histological thin-sectioning. Using femur length as covariate to account for differences in body size, analyses of covariance on cross sectional area, second moment of area, and polar moment of inertia revealed no significant differences among oxygen treatment groups. Combined allometric analyses of all groups showed that cross-sectional area scaled with significant positive allometry and that all moments of inertia scaled with significant negative allometry. We hypothesize that the right-left shunt in the alligator heart allows the maintenance of optimal oxygen saturation across a range of ambient oxygen levels. Our result suggest that atmospheric oxygen may have negligible influence on basal archosaur bone structure.